In order to determine the optimum combination of compressor pressure ratio and turbine- inlet temperature on the basis of load range for flight speeds in the transonic range, an analysis was made of the performance and the load-range characteristics of the turbojet engine for flight speeds from 500 to 800 miles per hour, altitudes from 10,000 to 70,000 feet, compressor pressure ratios from 2 to 30, and turbine-inlet temperatures of 1700, 2000, and 2300 degrees R.